Coastal erosion threatens archaeological sites in Libya

The study suggests that the archaeological sites of Apollonia, Ptolemais, and Tocra are at risk of extensive erosion.

The coastline of Cyrenaica (eastern Libya), stretching from the Gulf of Sirte to the present-day Egypt-Libya border, is rich in archaeological sites that span from the Palaeolithic through to the Byzantine period.

A recent study, however, has highlighted how rapidly increasing rates of coastal erosion and flooding are threatening the survival of important archaeological remains.

Drone image taken in 2022 showing damage to archaeological structures at the ancient harbour of Apollonia caused by coastal erosion. IMAGE: Saad Buyadem, CC-BY 4.0

Cyrenaica societies were trading with Mediterranean civilisations during the early Bronze Age.

In the 7th century BC, Greek settlers arrived and established the large inland settlement of Cyrene, as well as the coastal towns of Apollonia (the harbour of Cyrene), Taucheira (Tocra), and Ptolemais.

Cyrenaica was under Ptolemaic rule from 322 BC to 96 BC, before falling under Roman control. After AD 385, it became a part of the Byzantine Empire.

The region’s maritime trade links later collapsed following the Arab conquest (AD 642-645), and its successful coastal port cities fell into decline.

Evidence of erosion at Apollonia. Image A shows the erosion of the Roman road (decumanus) in front of the Byzantine structures (2019, S. Buyadem); image B, the eroding edge in front of Byzantine structures and a Roman bath (2021, F. El-Gumati); image C, the eroding edge in front of the insula, as well as undocumented buildings and mosaics are eroding out (2021, F. El-Gumati); and image D, an example of a mosaic floor exposed by erosion (2019, S. Buyadem).
Images: Westley et al., 2023, PLOS ONE, CC-BY 4.0

There has been little archaeological exploration or documentation at many of these sites – though this is changing with the launch of the Cyrenaica Coastal Survey (CCS) – and coastal erosion is expected to accelerate due to climate change and human actions, such as sand mining and urbanisation, raising uncertainties over their future survival.

Combining historical and modern records of the Cyrenaica shoreline, researchers have been able to identify and assess patterns of coastal erosion near important archaeological sites.

The team, led by Kieran Westley and Julia Nikolaus of Ulster University, compared aerial and satellite imagery of the shorelines at different time intervals using the Digital Shoreline Analysis System (DSAS), and then quantified the rates and magnitude of shoreline movement.

They found that, if present-day rates of erosion continue, the coastlines at the sites of Apollonia, Ptolemais, and Tocra are at risk of extensive erosion.

At Tocra, it is expected that an already-eroded proteichisma (curtain wall) from the Hellenstic period will suffer further damage, and that a nearby roofed cistern – originally a subterranean structure that has been exposed by the loss of beach sediment – will be entirely lost.

Image A shows the eroding cliffline west of Ptolemais (2021: CCS Survey); image B, structural material eroding out of the cliffline (2021: CCS Survey); image C, archaeological features exposed by wave action, and image D, exposed mosaic floors (2022: S. Buyadem). Images: Westley et al., 2023, PLOS ONE, CC-BY 4.0

Forts and harbour structures built in the 19th and 20th centuries during the Ottoman and Italian occupations of Libya are also being claimed by the sea.

At Apollonia, a paved Roman road (decumanus) is at risk of being fully worn away, and remains of a Roman bathhouse – particularly the entrance to the bath, the frigidarium, the latrines, and the aqueduct – will suffer significant erosion over the next 20 years.

Beyond the inland area of Ptolemais, only test excavations along its shoreline and limited surveying of the submerged harbour have been carried out.

This research revealed that archaeological remains around the ancient harbour – which include Roman villas with mosaic floors – may disappear within the next two decades.

The authors of the study, which has been published in PLOS ONE, call for urgent documentation of sites along the Cyrenaica coastline in order to preserve information about Libya’s past, especially concerning its involvement in ancient Mediterranean trade networks.